Lipid mediators are thought to contribute to a wide variety of pathophysiologic effects in the lung. Such molecules include arachidonate derivatives, i.e. the eicosanoids (5-lipoxygenase and cyclooxygenase pathways), and the ether phospholipid, platelet activating factor (PAF). Reasonable evidence has suggested that inflammatory cells and cells within the lung tissue itself communicate with each via such lipid substances and that the progression and outcome of inflammation and other altered states depends in part on the synthesis and disposition of these classes of compounds. The overall objective of this program project, therefore, is to investigate the regulation of lipid mediator biosynthesis and action in lung cells and in inflammatory cells. Specific objectives include: Determination of whether or not a unique precursor phospholipid (1-alkyl-2- arachidonoyl-GPC) exist for PAF and eicosanoids in inflammatory cells. Furthermore, that alteration of arachidonate remodeling within phospholipid membranes can alter eicosanoid and PAF biosynthesis. Characterization of a specific high molecular weight phospholipase A2 which uses 1-alkyl-2-arachidonoyl-GPC as substrate and is specifically involved in the release of arachiodonate from GPC. Fundamental studies of the biochemical processes and regulation of the uptake and release (secretion of lipid substances from the intracellular site of synthesis). Determine whether or not translocation of 5-lipoxygenase brings this critical enzyme to the exterior plasma membrane where it can process arachidonic acid into LTA4. From such a site of synthesis, LTA4 can then be processed by other cells into active mediators by transcellular biosynthesis. Investigate the mechanism of suicide inactivation of two enzymes, LTA4 hydrolase and thromboxane synthetase, both of which are involved at critical steps in lipid mediator biosynthesis. Investigate the role that PAF plays in lung parenchymal changes, fibrosis, and pulmonary hypertension in a model of chronic lung cell injury. Investigate the neutrophil dependent decrease in local blood flow to the lung and the role lipid mediators (thromboxane A2) play in this process. Examine the biosynthesis of acetylated phospholipids in the cells of the lung and inflammatory cells as a pathway for biosynthesis of active molecules. Extend the analytical capability for lipid mediators and their precursors by mass spectrometry. This program brings together investigators experience in cell biology, inflammation, pharmacology, physiology, lipid biochemistry, analytical chemistry, and clinical pulmonary medicine. This combination of structural, cellular, and physiologic approaches to a detailed analysis of the production of lipid mediators in the lung is felt to represent an important step in developing the ability to select control lipid mediator production and also eliminate pathologic events mediated by these molecules in vivo.